The present invention relates to a communications satellite repeater, and more precisely to such type of repeater which is used in a multibeam communications satellite having the flexibility in interbeam connections.
It is considered a multibeam communications satellite in which the same frequency is reused a number of times by the use of a number of spot beams or by the use of orthogonal polarizations.
In the conventional multibeam communications satellite, the satellite communications band is divided into channels each having, as a basic unit, a broad-bandwidth in the order of 40 MHz and a transponder is assigned to each of the channels. The structure of the communications satellite repeater used in a case where the number of beams is N and the number of channels is M will be shown in FIG. 1, for example.
In FIG. 1, Numeral 1 designates a receive antenna, Numeral 2 designates a receiver for performing amplification and frequency conversion, Numeral 3 designates input demultiplexers for dividing input beams into a plurality of channels, Numeral 4 designates a switch interconnecting each input channel to the desired output channel on a channel by channel basis, Numeral 5 designates an amplifier, Numeral 6 designates output multiplexers for multiplexing output channels to output beams and Numeral 7 designates a transmit antenna. Although the switch 4 and the amplifier 5 are shown for the channel 1, those for the channels 2 through M are the same in structure.
However, the conventional satellite communications repeater of the above structure has had such drawbacks that since interbeam connections are made by switches on a channel by channel basis, it is necessary to establish different interbeam connections for each channel in order to enable an earth station in one beam to communicate with all the other earth stations in separate beams and, therefore, the number of channels must be increased as the number of beams increases, accordingly, the communications satellite loses the operational flexibility resulting in substantially lowered satellite capacity.